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What is the current through the bulb of a flashlight that has a resistance of 5.0 ohms if the flashlight is powered by a battery with an EMF of 4.5 volts?
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If we picture this bulb as part of a circuit, we know it’s connected in series with a power supply of 4.5 volts and that the bulb’s resistance is 5.0 ohms.
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Based on this, we want to solve for the value of the current, we can call it capital 𝐼, that runs through the bulb.
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Ohm’s law can help us solve for this current.
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It tells us that the potential difference in a circuit is equal to the product of the current and the resistance of the circuit.
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We can rearrange Ohm’s law to solve for the current which is what we want to solve for in our particular instance.
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It’s equal to potential divided by resistance.
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The voltage of 4.5 volts divided by the resistance of 5.0 ohms is equal to 0.90 amps.
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That’s the current that runs through the bulb of the flashlight.